Low-intensity daily smoking and cause-specific mortality in Mexico: prospective study of 150 000 adults

Abstract

Background Research is needed to determine the relevance of low-intensity daily smoking to mortality in countries such as Mexico, where such smoking habits are common. Methods Prospective study of 159 755 Mexican adults recruited from 1998–2004 and followed for cause-specific mortality to 1 January 2018. Participants were categorized according to baseline self-reported smoking status. Confounder-adjusted mortality rate ratios (RRs) at ages 35–89 were estimated using Cox regression, after excluding those with previous chronic disease (to avoid reverse causality). Results Among 42 416 men and 86 735 women aged 35–89 and without previous disease, 18 985 men (45%) and 18 072 women (21%) reported current smoking and 8866 men (21%) and 53 912 women (62%) reported never smoking. Smoking less than daily was common: 33% of male current smokers and 39% of female current smokers. During follow-up, the all-cause mortality RRs associated with the baseline smoking categories of <10 cigarettes per day (average during follow-up 4 per day) or ≥10 cigarettes per day (average during follow-up 10 per day), compared with never smoking, were 1.17 (95% confidence interval 1.10–1.25) and 1.54 (1.42–1.67), respectively. RRs were similar irrespective of age or sex. The diseases most strongly associated with daily smoking were respiratory cancers, chronic obstructive pulmonary disease and gastrointestinal and vascular diseases. Ex-daily smokers had substantially lower mortality rates than those who were current daily smokers at recruitment. Conclusions In this Mexican population, low-intensity daily smoking was associated with increased mortality. Of those smoking 10 cigarettes per day on average, about one-third were killed by their habit. Quitting substantially reduced these risks.

Association Between Smoking, Smoking Cessation, and Mortality by Race, Ethnicity, and Sex Among US Adults

“…However, the current vs never smoker mortality RR was highest among non-Hispanic White smokers (3.00; 95% CI, 2.91-3.10) and somewhat lower among individuals who identified as Black, Hispanic, and other non-Hispanic race and ethnicity, who smoked fewer cigarettes per day on average, were less likely to smoke daily, and began smoking at slightly older ages (as in prior studies). Nevertheless, mortality rates were substantially higher among individuals who smoked than among those who had never smoked, as reported in other studies of comparably low-intensity smoking . Whether these factors may also explain the somewhat greater relative risk of smoking-related diseases among women than among men, as observed in prior research, remains unclear.…”

“…Because information on smoking habits was collected at a single point in time, the impact of smoking cessation or reinitiation after recruitment could not be assessed. Prior studies have suggested that some smokers may quit during follow-up, whereas others (typically few) may begin smoking. Thus, both the true hazards of smoking and the true benefits of quitting may be underestimated in this study.…”

“…Nevertheless, mortality rates were substantially higher among individuals who smoked than among those who had never smoked, as reported in other studies of comparably low-intensity smoking. 20,21 Whether these factors may also explain the somewhat greater relative risk of smoking-related diseases among women than among men, as observed in prior research, 2,22,23 remains unclear. a Attributable fractions were calculated as the fraction of deaths estimated to be attributable to smoking among ever smokers.…”

“…Prior studies 16,20,27 have suggested that some smokers may quit during follow-up, whereas others (typically few) may begin smoking. Thus, both the true hazards of smoking and the true benefits of quitting may be underestimated in this study.…”

Cancer mortality predictions for 2021 in Latin America

“…Latin American populations reported low-intensity daily smoking (on average less than 10 cigarettes per day vs. 15–20 per day in high-income countries) and higher smoking cessation rates. This is particularly evident in Mexico, which had the lowest lung cancer rates ( Thomson et al , 2021 ). The prevalence of current cigarette smokers (heavy and passive smokers, as well) decreased among Brazilian adults since 2006, with some slowdown in decreases over more recent periods ( Maia et al , 2021 ).…”